Objective: Our aim was to evaluate the efficacy of stereotactic radiosurgery (SRS) for the treatment of patients with brain metastases that have been determined to be "radioresistant" on the basis of histological examination.
Methods: We reviewed the medical records of 41 consecutive patients who presented with 83 brain metastases from radioresistant primaries and subsequently underwent SRS. All patients were followed until death or for a median of 31 months after SRS. Tumor histologies included renal cell carcinoma (16 patients), melanoma (23 patients), and sarcoma (2 patients). Eighteen patients (44%) had a solitary metastasis, and 23 patients (56%) had multiple metastases.
Results: The median overall survival time was 14.2 months after SRS. On the basis of univariate analysis, systemic disease status (P = 0.006) and Radiation Therapy Oncology Group recursive partitioning analysis (RPA) class (P = 0.005) were associated with survival. The median survival time was 23.5 months for patients in RPA Class I status and 10.5 months for patients in RPA Class II or III status. There was a trend (P = 0.12) toward improved median survival for patients with renal cell carcinoma (17.8 mo) as compared with patients with melanoma (9.7 mo). Multivariate analysis showed RPA class (P = 0.038) and histological diagnosis of primary tumor (P < 0.001) to be independent predictors for overall survival. In the 35 patients who underwent follow-up imaging, 9 (12%) of 73 tumors recurred locally. In 54% of the patients, distant brain failure (DBF) developed. Whole brain radiotherapy (WBRT) improved local control and decreased DBF, according to the univariate and multivariate analyses. Patients who received adjuvant WBRT in addition to SRS had 6-month actuarial local control of 100% as compared with 85% among those who did not receive WBRT (P = 0.018). Patients who received adjuvant WBRT with SRS had a 6-month actuarial DBF rate of 17%, as compared with a rate of 64% among patients who had SRS alone (P = 0.0027).
Conclusion: Well-selected patients with brain metastases from radioresistant primary tumors who undergo SRS survive longer than historical controls. RPA Class I status and primary renal cell carcinoma predict longer survival. Adjuvant WBRT improves local control and decreases DBF but does not affect overall survival. Further studies are needed to determine which patients should receive WBRT.